Systems are available which provide targeted advertising within web pages, for example in the form of banner advertisements or links to other web pages. By targeting the advertisements, such that they relate to the content of a page on which they are displayed or to keywords which have been used for searching, the advertisements are more likely to be relevant to the user and the advertiser is willing to pay more for the placement of the advertisement.
The systems which provide targeted advertising use crawling to categorize web sites. This is a lengthy process by which huge numbers of web pages are analyzed and categorized and the resultant information is stored in a database. In some cases the advertising is tailored based on the individual user's browsing behavior and this behavior may be tracked using a cookie which is downloaded to the user's computer from a web site which they visit. Additional software may also be delivered which creates a log of the user's browsing activity which may then be returned to the system along with the cookie. Characteristics of the user may be determined based on the stored categorization data for those web sites visited by the user.
In order that an advertisement can be included within a web page, the web site publishers manually insert a tag in the web page which acts as a placeholder for the targeted advertisement. The tag is then replaced with a selected advertisement when the user requests the page, where the advertisement is selected based on stored data, which may comprise the user's browsing activity log and/or the categorization of web pages. The knowledge of the person's behavior may be stored by the advertising company and the only information on the browser side may be an ID which is linked to the information in the advertising company's database.